CN103983260A - Method capable of effectively inhibiting quadrature errors of electrostatically actuated capacitive micro-machined gyroscope - Google Patents

Abstract

The invention provides a method capable of effectively inhibiting quadrature errors of an electrostatically actuated capacitive micro-machined gyroscope. One path of a gyroscope driving signal becomes a first demodulation reference signal after passing through a phase shifter, the first demodulation reference signal carries out secondary phase-sensitive demodulation on an input signal, and an obtained signal undergoes low pass filtering and is then output as a final output signal; the other path of the gyroscope driving signal becomes another demodulation reference signal orthogonal with the first demodulation reference signal after passing through the same phase shifter and a 90-DEG phase shifter, then the demodulation reference signal carries out secondary phase-sensitive demodulation on the input signal, and an obtained signal undergoes low pass filtering and is then used as an input signal Vout7 of a differentiating circuit; output of the differentiating circuit is used as a control signal for the phase shifters, and when the control signal is zero, the phase shifters stop working and the phase shift values of the phase shifters maintain unchanged; and when the control signal is not zero, the phase shifters continue working until the output of the differentiating circuit is zero. The method provided by the invention can effectively reduce quadrature errors of the electrostatically actuated capacitive micro-machined gyroscope during detection of angular velocity caused by process errors and substantially improve measurement accuracy of the electrostatically actuated capacitive micro-machined gyroscope.

Description

A kind of static electricity driving capacitor mechanical gyroscope that declines effectively suppresses the method for quadrature error

Technical field

The present invention relates to a kind of static electricity driving capacitor mechanical gyroscope that declines and effectively suppress the method for quadrature error, can eliminate to a great extent the impact of quadrature error on useful angular velocity, make gyrostatic measurement result more accurate.

Background technology

At present, there is many deficiencies in the inhibition method of micro-mechanical gyroscope quadrature error.Even if gyro is a kind of sensor that also can detect moving object self attitude and state variation without extraneous reference signal, its function is the angular velocity of perceive motion body.The initial stage nineties, along with the fast development of micromachining technology, the third generation micro-mechanical gyroscope based on MEMS technology has been born, this gyroscope have volume little, lightweight, be with the advantages such as roomy, low in energy consumption, impact strength is high, therefore, be widely used in military affairs, civil area.

The sensitive structure of micro-mechanical gyroscope adopts silicon or surface silicon processes to be made, and because size is extremely small, is generally micron dimension, under existing process conditions, is difficult to controlled working precision.Therefore, sensitive structure exists fabrication error in manufacture process.These errors will directly affect the stability of silicon micromechanical gyroscope output at zero point, the key technical index such as nonlinearity, bandwidth of operation of scaling factor.This has also restricted the application of micromechanical gyro in needs accurate measured angular rate signal fields such as aerospace, precise guidance, exact instrument, deep-sea detectings.The various fabrication errors of sensitive structure can be transformed into two kinds of error signals, i.e. quadrature error and in-phase error in the processing procedure of micro-mechanical gyroscope extraction angular velocity signal.

The quadrature error of micro-mechanical gyroscope and in-phase error are two kinds of main undesired signals in angular velocity signal leaching process, and they derive from the process of micromechanical gyro sensitive structure, are the principal elements of restriction micromechanical gyro overall performance.In signal processing, reduce or eliminate these two kinds of error signals and be not subject to the restriction of processing technology, highly versatile, is a kind of very effective technical method.Chinese scholars research in this respect has at present obtained certain achievement, but also exists many shortcoming, is mainly manifested in:

1, while utilizing combined synchronous demodulation technique to eliminate quadrature error, actual signal will inevitably produce phase error because of transmission delay in processing procedure, therefore require reference signal and signal phase to be demodulated to equate very difficult realization completely, this has also caused in actual applications, and quadrature error signal can not be eliminated completely by synchronous demodulation method.

If 2 adopt electrostatic force feedback to form closed-loop system to suppress quadrature error, because the extraction of quadrature error is to be based upon in the situation that the phase place of reference signal and signal to be demodulated just in time differs 90 °, and it is very difficult to meet this condition, how extracting pure quadrature error signal or eliminating as much as possible phase error is technological difficulties, also there is no at present corresponding solution.

Summary of the invention

In order to overcome above-mentioned deficiency, the invention provides a kind of static electricity driving capacitor mechanical gyroscope that declines and in the time that signal is processed, eliminate or effectively suppress the method for quadrature error, supplement as the useful of micromechanical gyro angular velocity signal extracting method, instruct interface circuit design, can be in completing angular velocity signal extraction, the impact of compensation quadrature error signal on useful Coriolis acceleration signal, thereby improve the stability of micromechanical gyro output at zero point, the nonlinearity of scaling factor, the key technical index such as bandwidth of operation, improve significantly the overall performance of silicon micromechanical gyroscope, reach the object of utilizing signal processing compensate for process error.

A kind of static electricity driving capacitor of the present invention mechanical gyroscope that declines effectively suppresses the method for quadrature error, specifically comprises the steps:

Step 1, angular velocity extract the charge amplifier that circuit utilization is made up of integrator, the changing value of capacitive micro mechinery gyroscope instrument sensitive structure Detection capacitance is transformed into voltage signal, to after this voltage signal filter and amplification, obtain through phase demodulation for the first time the voltage signal being directly proportional to the variable quantity of Detection capacitance, then through low-pass filtering with amplify after obtain input signal V _in(t);

Step 2, gyroscope drive signal one tunnel after phase shifter, directly to become first via demodulated reference signal V _ref3(t), to input signal V _in(t) carry out for the second time after phase demodulation, then through low-pass filtering as final output signal V _out8output;

Step 3, gyroscope drive after the phase shifter and 90 ° of phase shifters that another Lu Jingyu step 2 of signal is identical, become and first via demodulated reference signal V _ref3(t) orthogonal demodulated reference signal V _ref4(t), to input signal V _in(t) carry out for the second time after phase demodulation, then export differentiating circuit to through low-pass filtering, as the input signal V of differentiating circuit _out7;

The output of step 4, differentiating circuit is as the control signal of described phase shifter, in the time that control signal is zero, phase shifter quit work and its phase shift value constant; In the time that control signal is non-vanishing, described phase shifter will work on until differentiating circuit is output as at 1 o'clock, the feedback system being made up of differentiating circuit and phase shifter is stable at Δ φ=0, this Δ φ is the phase error that signal processing is introduced, only has in the time of phase error af=0 output signal V _out8in quadrature error because phase error af=0 is eliminated.

Adopt the present invention a kind of static electricity driving capacitor mechanical gyroscope that declines effectively to suppress the method for quadrature error, can effectively reduce the static electricity driving capacitor quadrature error that mechanical gyroscope causes due to fabrication error in the time detecting angular velocity that declines.According to theoretical analysis, in the time that phase error is zero, if the reference signal of phase demodulation is to drive signal for the second time, the signal after demodulation will not comprise quadrature error signal; If the reference signal of phase demodulation and driving signal in orthogonal for the second time, the signal after demodulation will contain pure quadrature error signal and not comprise angular velocity and in-phase error signal.The present invention designs the signal processing method of corresponding inhibition quadrature error according to above situation, can effectively reduce its impact on useful angular velocity, greatly improves the decline measuring accuracy of mechanical gyroscope of static electricity driving capacitor.

Brief description of the drawings

Fig. 1 is that the present invention suppresses quadrature error (phase error is 0) schematic diagram;

Fig. 2 is the extraction schematic diagram of micro-mechanical gyroscope angular velocity signal of the present invention.

Below in conjunction with the drawings and specific embodiments, the invention will be further described.

Embodiment

As shown in Figure 2, from the principle of work of micro-mechanical gyroscope, the numerical value of input angular velocity signal be obtained, the variable quantity of sensitive structure Detection capacitance must be measured.But, the variable quantity of Detection capacitance is extremely faint, conventionally be all submerged in the 1/f noise of low frequency, in order to suppress 1/f noise, angular velocity extracts the method that circuit adopts high frequency carrier to modulate, and utilizes the charge amplifier being made up of integrator, and the changing value of Detection capacitance is transformed into voltage signal, then through twice phase demodulation process, phase demodulation obtains the voltage signal being directly proportional to the variable quantity of Detection capacitance for the first time; Demodulation for the second time obtains the voltage signal being directly proportional to input angular velocity signal.

(1) Output Signal Analysis while considering quadrature error and in-phase error under the prerequisite that does not have phase error:

As shown in Figure 1, for the first time after phase demodulation, the voltage signal V obtaining _in(t) be directly proportional to the variable quantity of Detection capacitance, ideally, this voltage signal V _in(t) in, only comprise angular velocity signal; If when the quadrature error of existence and in-phase error, this V _in(t) be angular velocity signal, quadrature error and in-phase error three sum, can be expressed as follows:

V _in(t)=V _cor·Ω·cos(ωt+φ)+V _in-p·cos(ωt+φ)+V _quc·sin(ωt+φ) (1)

Wherein, V _correpresent the amplitude of Coriolis acceleration signal; V _in-prepresent the amplitude of in-phase error; V _qucrepresent the amplitude of quadrature error; Ω represents the angular velocity signal of input; ω represents that micro-mechanical gyroscope drives the angular frequency of signal; φ represents to drive the phase place of signal.From formula (1), can find out that in-phase error all equates with Coriolis acceleration signal frequency and phase place, and quadrature error equates with Coriolis acceleration signal frequency, 90 ° of phase phasic differences.

If there is not phase error, the reference signal V of phase demodulation for the second time _ref(t) be exactly to drive signal, it and V _in(t) carry out multiplying, computing is as follows:

$\begin{array}{c}{V}_{\mathrm{in}}\left(t\right)\·V_{\mathrm{ref}}\left(t\right)=(V_{\mathrm{cor}}\·V_d\·\mathrm{\Ω}\·+V_{\mathrm{in}-\·p}\·V_d)\·{\cos }^2(\mathrm{\ωt}+\mathrm{\φ})+V_{\mathrm{quc}}\·V_d\·\cos (\mathrm{\ωt}+\mathrm{\φ})\·\sin (\mathrm{\ωt}+\mathrm{\φ})\\ =\frac{1}{2}(V_{\cot }\·V_d\·\mathrm{\Ω}\·+V_{\mathrm{in}-p}\·V_d)+\frac{1}{2}(V_{\mathrm{cor}}\·V_d\·\mathrm{\Ω}\·+V_{\mathrm{in}-p}\·V_d)\cos (2\mathrm{\ωt}+2\mathrm{\φ})+\frac{1}{2}{V}_{\mathrm{quc}}\·V_d\·\mathrm{isn}(2\mathrm{\ωt}+2\mathrm{\φ})\end{array}---\left(2\right)$

Eliminating frequency through low-pass filtering is the high frequency item of 2 ω, the output signal V obtaining _out1(t) be:

$V_{\mathrm{out}1}\left(t\right)=\frac{1}{2}(V_{\mathrm{cor}}\·V_d\·\mathrm{\Ω}\·+V_{\mathrm{in}-p}\·V_d)---\left(3\right)$

Conclusion: if the reference signal V of phase demodulation for the second time _ref(t) during for driving signal, comprise angular velocity signal and in-phase error signal in final output signal, quadrature error is completely eliminated;

If the reference signal V of phase demodulation for the second time _ref(t) with driving signal in orthogonal, be also that its expression formula is V _ref(t)=V _dsin (ω t+ φ), by it and V _in(t) carry out multiplying, computing is as follows:

$\begin{array}{c}{V}_{\mathrm{in}}\left(t\right)\·V_{\mathrm{ref}}\left(t\right)=(V_{\mathrm{cor}}\·V_d\·\mathrm{\Ω}\·+V_{\mathrm{in}-p}\·V_d)\·\cos (\mathrm{\ωt}+\mathrm{\φ})\·\sin (\mathrm{\ωt}+\mathrm{\φ})+V_{\mathrm{quc}}\·V_d\·{\sin }^2(\mathrm{\ωt}+\mathrm{\φ})\\ =\frac{1}{2}(V_{\mathrm{cor}}\·V_d\·\mathrm{\Ω}\·+V_{\mathrm{in}-p}\·V_d)\sin (2\mathrm{\ωt}+2\mathrm{\φ})-\frac{1}{2}{V}_{\mathrm{quc}}\·V_d\cos (2\mathrm{\ωt}+2\mathrm{\φ})+\frac{1}{2}{V}_{\mathrm{quc}}\·V_d\end{array}---\left(4\right)$

Eliminating frequency through low-pass filtering is the high frequency item of 2 ω, the output signal V obtaining _out2(t) be:

$V_{\mathrm{out}2}\left(t\right)=\frac{1}{2}{V}_{\mathrm{que}}\·V_d---\left(5\right)$

Conclusion: if the reference signal V of phase demodulation for the second time _ref(t), during with driving signal in orthogonal, final output signal is pure quadrature error signal.

(2) Output Signal Analysis while considering quadrature error and in-phase error under the prerequisite that has phase error:

AC signal will inevitably cause the skew of phase place in transmission and processing process, and therefore in reality, phase error is difficult to avoid, thus should take in the situation of phase error existence, in the time considering phase error, the voltage signal V obtaining after phase demodulation for the first time _in(t) need represent with following equation:

V _in(t)=V _cer·Ω·cos(ωt+φ+Δφ)+V _in·p·cos(ωt+φ+Δφ)+V _que·sin(ωt+φ+Δφ) (6)

Δ φ is the phase error that signal processing is introduced in formula (6), now to drive signal as the reference signal V of phase demodulation for the second time _ref(t), the final output signal after low-pass filtering is:

$V_{\mathrm{out}8}=\frac{1}{2}(V_{\mathrm{cor}}\·V_d\·\mathrm{\Ω}+V_{\mathrm{in}-p}\·V_d)\cos \mathrm{\Δ\φ}+\frac{1}{2}{V}_{\mathrm{quc}}\·V_d\sin \mathrm{\Δ\φ}---\left(7\right)$

Comparison expression (7) is known with formula (3), in the time there is phase error, if the reference signal of phase demodulation is for driving signal for the second time, in final output signal, comprise angular velocity and in-phase error signal, also comprise quadrature error signal, phase error af is less, and sin Δ φ more levels off to zero, and quadrature error signal is also less.

If the reference signal V of phase demodulation for the second time _ref(t) with driving signal in orthogonal, be also that its expression formula is V _ref(t)=V _dsin (ω t+ φ), now the final output signal after low-pass filtering is:

$V_{\mathrm{out}7}=\frac{1}{2}{V}_{\mathrm{quc}}\·V_d\cos \mathrm{\Δ\φ}-\frac{1}{2}(V_{\mathrm{cor}}\·V_d\·\mathrm{\Ω}+V_{\mathrm{in}-p}\·V_d)\sin \mathrm{\Δ\φ}---\left(8\right)$

Comparison expression (8) is known with formula (5), in the time there is phase error, if when the reference signal Vref of phase demodulation (t) is with driving signal in orthogonal for the second time, in final output signal, comprise quadrature error signal, also comprise angular velocity and in-phase error signal, phase error af is less, and sin Δ φ more levels off to zero, and angular velocity and in-phase error signal are also less.

Conventionally angular velocity Ω is a time dependent amount, V _out7in also be a time dependent amount, V _out7in remaining two with can think constant DC quantity.If Δ φ=0, V _out7should be DC quantity, on the contrary Δ φ ≠ 0 because angular velocity Ω changes, V _out7not not just DC quantity.Δ φ=0 o'clock V _out8in quadrature error be zero.V _out7be DC quantity, its derivative should equal zero, and has following formula to set up:

$\frac{{\mathrm{dV}}_{\mathrm{out}7}\left(t\right)}{\mathrm{dt}}{=0|}_{\mathrm{\Δ\φ}=0}---\left(9\right)$

Can design a feedback control system that comprises phase shifter and differentiating circuit based on the above fact, phase shifter carrys out the poor Δ φ of control phase by the phase place of controlling demodulated reference signal, and differentiating circuit is used for V _out7ask single order to lead to determine V _out7whether be DC quantity.V _out7signal after differentiating circuit is as the control signal of phase shifter, this control signal be 1 o'clock phase shifter quit work and its phase shift value constant, when control signal is non-vanishing phase shifter will work on until differentiating circuit be output as at 1 o'clock also system stability in Δ φ=0, now V _out8in quadrature error $\frac{1}{2}{V}_{\mathrm{quc}}\·V_d\mathrm{\Ω}\·\sin \mathrm{\Δ\φ}$ Just do not exist.

As shown in Figure 1, a kind of static electricity driving capacitor of the present invention mechanical gyroscope that declines effectively suppresses the method for quadrature error, specifically comprises the steps:

Step 1, angular velocity extract the charge amplifier that circuit utilization is made up of integrator, the changing value of capacitive micro mechinery gyroscope instrument sensitive structure Detection capacitance is transformed into voltage signal, to after this voltage signal filter and amplification, obtain through phase demodulation for the first time the voltage signal being directly proportional to the variable quantity of Detection capacitance, then through low-pass filtering with amplify after obtain input signal V _in(t);

Step 2, gyroscope drive signal one tunnel after phase shifter, directly to become first via demodulated reference signal V _ref3(t), to input signal V _in(t) carry out for the second time after phase demodulation, then through low-pass filtering as final output signal V _out8output;

Step 3, gyroscope drive after the phase shifter and 90 ° of phase shifters that another Lu Jingyu step 2 of signal is identical, become and first via demodulated reference signal V _ref3(t) orthogonal demodulated reference signal V _ref4(t), to input signal V _in(t) carry out for the second time after phase demodulation, then export differentiating circuit to through low-pass filtering, as the input signal V of differentiating circuit _out7;

The output of step 4, differentiating circuit is as the control signal of described phase shifter, in the time that control signal is zero, phase shifter quit work and its phase shift value constant; In the time that control signal is non-vanishing, described phase shifter will work on until differentiating circuit is output as at 1 o'clock, the feedback system being made up of differentiating circuit and phase shifter is stable at Δ φ=0, this Δ φ is the phase error that signal processing is introduced, only has in the time of phase error af=0 output signal V _out8in quadrature error because phase error af=0 is eliminated.

The above, it is only preferred embodiment of the present invention, not technical scope of the present invention is imposed any restrictions, therefore any trickle amendment, equivalent variations and modification that every foundation technical spirit of the present invention is done above embodiment all still belong in the scope of technical solution of the present invention.

Claims (1)

1. the static electricity driving capacitor mechanical gyroscope that declines effectively suppresses the method for quadrature error, it is characterized in that comprising the steps:

Step 1, angular velocity extract the charge amplifier that circuit utilization is made up of integrator, the changing value of capacitive micro mechinery gyroscope instrument sensitive structure Detection capacitance is transformed into voltage signal, to after this voltage signal filter and amplification, obtain through phase demodulation for the first time the voltage signal being directly proportional to the variable quantity of Detection capacitance, then through low-pass filtering with amplify after obtain input signal V _in(t);

Step 2, gyroscope drive signal one tunnel after phase shifter, directly to become first via demodulated reference signal V _ref3(t), to input signal V _in(t) carry out for the second time after phase demodulation, then through low-pass filtering as final output signal V _out8output;

Step 3, gyroscope drive after the phase shifter and 90 ° of phase shifters that another Lu Jingyu step 2 of signal is identical, become and first via demodulated reference signal V _ref3(t) orthogonal demodulated reference signal V _ref4(t), to input signal V _in(t) carry out for the second time after phase demodulation, then export differentiating circuit to through low-pass filtering, as the input signal V of differentiating circuit _out7;

The output of step 4, differentiating circuit is as the control signal of described phase shifter, in the time that control signal is zero, phase shifter quit work and its phase shift value constant; In the time that control signal is non-vanishing, described phase shifter will work on until differentiating circuit is output as at 1 o'clock, the feedback system being made up of differentiating circuit and phase shifter is stable at Δ φ=0, this Δ φ is the phase error that signal processing is introduced, only has in the time of phase error af=0 output signal V _out8in quadrature error because phase error af=0 is eliminated.